In order to improve network coverage and communication capacity of a system, the 3rd Generation Partnership Project (3GPP) is currently studying the deployment of a Small cell in a Long Term Evolution-Advanced (LTE-A) system. As compared with a Macro evolved NodeB (eNB), the so-called Small cell has a main feature of low radio frequency (RF) transmission power, so its coverage is usually smaller than the Macro eNB. Generally, the Small cell is deployed within the existing coverage of the Macro eNB. Depending on different topographic conditions and user requirements, one or more Small cells may be deployed at a particular region, so as to enhance the network coverage, enable radio resource reuse, and increase the system capacity.
In the case that a user is currently located within the coverage of the Macro cell and the Small cell, a Radio Resource Control (RRC) connection with the two base stations may be maintained by the user simultaneously, i.e., the Macro cell and the Small cell may provide services to the user simultaneously and two physical communication links to the Macro cell and Small cell may be maintained by the user. In the case that the two base stations provide services to the user simultaneously, one of them serves as a Master eNB (MeNB) while the other serves as a Slave eNB (SeNB). Usually, the MeNB assists the management of user-control-plane-related information, while the SeNB mainly takes charge of providing radio resources to a User Equipment (UE). Such network architecture is usually called as dual connection. Through the dual-connection technique, it is able to effectively increase uplink and downlink rates for the UE as well as the system capacity. In addition, this technique also has such advantages as signaling optimization and mobility robustness enhancement. FIG. 1 shows a typical dual-connection network architecture, where a terminal may receive signals from the Macro cell and the Small cell simultaneously, and backhaul services may be provided between the Macro cell and the Small cell.
Currently, in the case of the dual connection, a user control plane is managed by the MeNB, and the SeNB mainly takes charge of providing the radio resources for a user plane, as shown in FIG. 2, where dotted lines represent the information transmission for the user plane, while solid lines represent the information transmission for the control plane.
For the dual-connection mechanism, especially in the case that an identical user is served by two base stations, there is an urgent need to find a way to establish the dual connection for the UE. As an initial proposal, after the UE accesses a network via the MeNB, the MeNB may determine whether or not the dual connection is to be established for the UE. In the case that the MeNB determines to establish the dual connection for the UE, it may request the SeNB to provide resources for the UE, or in the case that the SeNB determines to adjust the physical resources previously provided for the UE, it may request the MeNB to modify a dual-connection configuration for the UE again, FIG. 3 shows a specific process which includes the following steps.
Step S300a: the MeNB determines to establish the dual connection for the UE, or Step S300b: the SeNB modifies the dual-connection configuration previously provided for the UE.
Step S302: the MeNB requests the SeNB to add or modify the dual-connection configuration for the UE.
Step S304: the SeNB performs operations such as admission control in accordance with its own resource condition.
Step S306: the SeNB sends a message to the MeNB to confirm the dual-connection configuration for the UE.
Step S308: the MeNB notifies the UE of the dual-connection configuration.
Step S310: the MeNB notifies the SeNB of user data state information that needs to be transmitted by the SeNB.
Step S312: the MeNB forwards to the SeNB the user data that needs to be transmitted by the SeNB.
Step S314: after the completion of the dual-connection configuration, the UE sends an acknowledgement message to the MeNB.
Step S316: the UE establishes a radio connection with the SeNB.
Step S318: the SeNB notifies the MeNB that a new connection has been established between the UE and the SeNB.
Step S320: the MeNB notifies a Mobile Management Entity (MME) that some data carriers for the UE have been switched to the SeNB.
Step S322: the MME notifies a Serving-Gateway (SGW) that some data carriers for the UE have been switched to the SeNB.
In the related art, in the case that the MeNB establishes or modifies the dual-connection configuration for the UE, the SeNB is considered to have the ability to admit the requirements on the radio resources by default. However, during the actual network deployment, the SeNB, for various reasons, may not provide sufficient resources. At this time, abnormalities may occur at a network side in the case that the MeNB establishes or modifies the dual-connection configuration for the UE using a conventional mode, and the UE does not know how to process the services for which insufficient resources are provided. In addition, in the case that the MeNB requests the SeNB to provide the radio resource configuration to establish the dual connection for the UE, it may probably requests a small quantity of resources, but the SeNB may provide more available resources. At this time, a waste of resources may occur, and thereby the resource utilization rate may be reduced.
However, there is currently no mechanism to handle the above-mentioned problems. In other words, for the radio resources capable of being provided for the UE as the dual connection configuration, a feasible mechanism needs to be provided to the MeNB and the SeNB, so as to coordinate the radio resources between the MeNB and the SeNB, thereby to optimize the use of the radio resources between different network nodes and handle the possible abnormalities.